1. Field of the Invention
The present invention relates to a traction drive type continuously variable transmission that continuously changes an input-output gear ratio.
2. Description of the Related Art
Conventionally, for example, a ball planetary type continuously variable transmission disclosed in Japanese National Publication of International Patent Application No. 2012-506001 and Japanese Patent Application Laid-open No. 2012-225390 is known. The continuously variable transmission includes three power transmission components (two disks or two rings and a sun roller) which have a common rotation axis, rolling components (planet balls) which are radially disposed with respect to the rotation axis and are sandwiched by the three power transmission components, and holding components (carriers) which respectively hold the planet balls in a tiltable and spinnable manner through both ends of a support shaft. Each holding component includes two disk-shaped plates of which the center axes match the rotation axis. In the continuously variable transmission disclosed in Japanese National Publication of International Patent Application No. 2012-506001, one plate (a rotation plate) is rotated with respect to the other plate (a fixed plate) about the rotation axis, so that each rolling component is tilted along with each support shaft. For this reason, the fixed plate is provided with a guide portion which guides one end of the support shaft in the radial direction of the plate. Further, the rotation plate is provided with a gear change portion (that is, the gear change portion which tilts the guide portion of the fixed plate in the circumferential direction of the plate) of which the longitudinal direction is tilted in the circumferential direction of the plate with respect to the radial direction of the plate. The other end of the support shaft is inserted into the gear change portion and moves along the gear change portion with the rotation of the rotation plate. Further, in the continuously variable transmission disclosed in Japanese Patent Application Laid-open No. 2012-225390, a different fixed plate is provided between the rotation plate and each rolling component so as not to be rotatable as in the fixed plate. The different fixed plate is provided with a guide portion which guides the other end of the support shaft in the radial direction.
In such a continuously variable transmission, a fixed plate is provided between the rotation plate and each rolling component. Therefore, a skew generated by a deviation of the rotation axes of the rolling components is not generated because of the two fixed plates, and a gear ratio cannot be assured during normal rotation. In that case, it can be considered that the fixed plate provided between the rotation plate and each rolling component is made rotatable to generate a skew for assuring the gear ratio during the normal rotation. However, if the fixed plate is made rotatable, when the rotation directions of the first and second power transmission components are reversed, the forces applied therebetween do not match each other. For this reason, a divergence in skew angle occurs. As a result, there is a possibility that the rotation of the support shaft of the rolling component may be locked, for example, because the support shaft of the rolling component moves along the guide portion, an inclination angle thereof becomes maximum, and therefore, a ball support shaft on a fixed carrier side might be bitten into a bottom of the guide portion. That is, there is a possibility that the power may not be transmitted or the gear ratio may not be changed after the transmission of the power during the reverse rotation of the first and second power transmission components.